Drunk brute

Geneticists have established the reason why elephants and armadillos get drunk easily

Marina Astvatsaturyan, Echo of Moscow

Elephants, narwhal whales and guinea pigs are among the mammals that have been found to have 10 independent breakdowns that occurred during evolution in the gene that encodes the enzyme alcohol dehydrogenase 7 (ADH7), according to a press release Elephants get drunk because they can't metabolize alcohol like us.

The ability of different mammalian species to metabolize alcohol was studied by a group of scientists led by Mareike Janiak from the Canadian University of Calgary, the authors of an article in the journal Biology Letters (Janiak et al., Genetic evidence of widespread variation in ethanol metabolism among mammals: revisiting the ‘myth' of natural intoxication).

The alcohol dehydrogenase gene plays a key role in this process and most mutations on it lead to the accumulation of alcohol in the blood of animals, therefore, to their more pronounced intoxication. Carnivorous cetaceans, herbivorous guinea pigs and most other animals identified in the study as potentially getting drunk quickly may not consume sweet fruits and nectar in which alcoholic fermentation takes place.

However, elephants eat fruit, and a new study returns to a long-standing dispute about the reality of intoxication of elephants who have eaten the fruits of the marula tree.

The first description of the strange behavior of elephants, who have a craving for overripe fruits, appeared in 1875. Later, in experiments where animals were offered water with an addition of ethanol, it was found that elephants choose it, and then move swaying and behave more aggressively. But in 2006, physiologist Steve Morris from the University of Bristol in England called the idea of elephant intoxication a "myth."

Among Morris's arguments were calculations based on the number of fermented marula fruits that African elephants are able to eat at one time, and they indicated that it was clearly not enough to get drunk.

However, the conclusions from those calculations were based on human physiology. The data published now on the non-functioning alcohol dehydrogenase gene of elephants means that they have a low tolerance to alcohol. After analyzing the available genetic information on 79 mammalian species, the authors found that the alcohol dehydrogenase IV (ADH IV) gene lost its function at 10 different points in the mammalian evolutionary tree. These are the branches on which elephants, armadillos, rhinoceroses, degu bush squirrels, beavers and bulls with cows are exposed to alcohol.

At the same time, in humans and anthropoid African primates, a mutation affecting this gene (ADH7) led to a 40-fold increase in the ability to break down alcohol compared to the level corresponding to the typical mammalian variant of alcohol dehydrogenase.

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